<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<canvas id="draw" width="600" height="600" style="background-color: #CCCCCC;"></canvas>
	
		<script>
		function draw(){
			 var canvas=document.getElementById("draw");
			 if(!canvas||!canvas.getContext) return;
			 var oContext=canvas.getContext("2d");
			 oContext.fillStyle="red";
			 oContext.
			 oContext.fillRect(10,10,550,550);
			 oContext.globalCompositeOperation="xor";
			 oContext.beginPath();
			 oContext.arc(250,250,230,0,2*Math.PI);
			 oContext.fill();
			 canvas.addEventListener()
		}
		draw();
		</script>
	
	</body>
</html>
